The present invention relates to a mounted circuit board producing system including a plurality of mounted circuit board production lines for mounting components on circuit boards.
A prior art example of a mounted circuit board production line for mounting components on circuit boards is described in Japanese Patent Application No. 4-260449 (published as Laid-Open Publication No. 6-112295), entitled "Mounted Circuit Board Producing System".
The prior art mounted circuit board production system of Japanese Patent Application No. 4-260449 is explained hereinbelow with reference to FIGS. 17 and 18, 7 through 16.
In FIG. 17, the mounted circuit board production line includes a solder printing unit 1, a component mounting unit 2, and a soldering unit 3 sequentially arranged therein.
Initially, a solder paste printing device 4 at the solder printing unit 1 prints solder paste on a land of a circuit board. Then, a mounting device 8 at the component mounting unit 2 mounts components in place so that leads for the components and electrodes are positioned on the solder paste printed lands. Finally, a reflow furnace 12 at the soldering section causes the solder paste to reflow to solder-joint the leads for the mounted parts and the electrodes to the land of the circuit board.
In connection with the foregoing operation, various inspections are carried out. A solder paste printing inspecting device 5 at the solder printing unit 1 performs inspection with respect to monitor items for the solder paste printed on the lands of the circuit board, including, for example, thin print, print shift (print displacement), and presence or absence of print solder, and also with respect to monitor items for the circuit boards and the solder paste printing device 4, including, for example, circuit board mark shift amount and screen mark shift amount.
A post-mounting component inspecting device 9 at the component mounting unit 2 performs inspection with respect to monitor items for components which are mounted on the circuit board by the mounting device 8, such as component lacking, component rising, component out of position, and component mounted with mispolarity, and also with respect to monitor items for the mounting device 8, such as suction error and recognition error at suction nozzle.
Further, a soldering inspecting device 13 at the soldering unit 3 performs inspection with respect to monitor items for soldered condition of components on the circuit board, such as component lacking, component rising, component out of position, and component mounted with mispolarity, and also inspection with respect to monitor items for the reflow furnace 12, such as heater temperature, conveyor velocity, and oxygen concentration.
On the basis of the results of the foregoing inspections, quality control is carried out by data holding parts 6, 10, 14 and data analyzing parts 7, 11, 15 of a control part 17, details of which are as follows.
For the solder printing unit 1, the printing data holding part 6 collects and holds inspection data on monitor items at the solder paste printing inspecting device 5, and the printing data analyzing part 7 carries out collective analyses and time series analyses, by monitor items, by circuits, and by equipment units, with respect to inspection data on monitor items which are held by the printing data holding part 6. Thus, as FIG. 18 shows, particulars as to equipment condition at, and quality aspect of circuit boards at the solder printing unit 1, are grasped on the basis of the results of comparison of data obtained from such analyses with predetermined warning criteria for respective monitor items.
For the parts mounting unit 2, the mounting data holding part 10 collects and holds inspection data on monitor items at the post-mounting component inspecting device 9, and the printing data analyzing part 11 carries out collective analyses and time series analyses, by monitor items, by circuits, and by equipment units, with respect to inspection data on monitor items which are held by the mounting data holding part 10. Thus, as FIG. 18 shows, particulars as to equipment condition at, and quality aspect of circuit boards at the component mounting unit 2, are grasped on the basis of the results of comparison of data obtained from such analyses with predetermined warning criteria for respective monitor items.
For the soldering unit 3, the soldering data holding part 14 collects and holds inspection data on monitor items at the soldering inspecting device 13, and the soldering data analyzing part 15 carries out collective analyses and time series analyses, by monitor items, by circuits, and by equipment units, with respect to inspection data on monitor items which are held by the soldering data holding part 14. Thus, as FIG. 18 shows, particulars as to equipment condition at, and quality aspect of circuit boards at the soldering unit 3, are grasped on the basis of the results of comparison of data obtained from such analyses with predetermined warning criteria for respective monitor items.
The manner of quality control operation according to the warning criteria shown in FIG. 18 will be explained hereinbelow. Between a normal region and an NG region beyond a criterion for judgement of defects there is established a warning criterion, and the region between the judgement criterion and the warning criterion is taken as a warning region. With respect to inspection data on a monitor item, a detection is made whether the data has entered the warning region across the warning criterion. In case of such an entry having been made, operation of equipment is controlled so that operation can quit the warning region to return to the normal region.
An example is shown in FIGS. 7 to 12.
FIG. 7 shows an example of print inspection error analysis by circuit numbers with respect to monitor items, such as soldering lack and soldering blur, at the solder printing unit 1, with warning criteria and judgement criteria established according to cumulative percentages of soldering lack and soldering blur cases which have entered the warning region. In the FIG. 7 case, circuit No. N413 whose cumulative percentage of entry into the warning region is highest of all is still outside the warning criteria. When such cumulative percentage has exceeded the warning criteria, maintenance instructions with respect to equipment and circuit boards are given to cause various checks to be carried out, including squeegee checks such as squeegee pressure and inclination checks, circuit board (PCB) checks such as land position accuracy and flatness checks, and screen checks such as position and pressing amount checks. Then, operation of equipment is modified so that the inspection results will come within the normal region.
FIG. 8 shows an example of time series analysis of inspection results with respect to monitor items for "soldering positional shift (in X direction)" at the solder printing unit 1, with warning criteria set at .+-.0.1 mm and judgement criteria at .+-.0.2 mm. Although measurement results are within the normal region in FIG. 8, circuit, when inspection measurements exceed the warning criteria, maintenance instructions with respect to the equipment and circuit boards are given to cause various checks to be carried out, including squeegee checks, circuit board checks, and temperature checks, and also to cause various operations to be executed, including print offset changing, adjustment of squeegee pressure, etc., and cleaning operation against screen blinding and the like. Then, operation of equipment is modified so that the inspection results will come within the normal region.
FIG. 9 shows an example of by-nozzle error rate with respect to monitor items, such as absence of suction, suction in oriented state, suction in rotating state, recognition error, and abnormal recognition, at the component mounting unit 2, with warning criteria and judgement criteria established according to cumulative percentages of such items as "absence of suction", "suction in oriented state", "suction in rotating state", "recognition error", and "abnormal recognition", which have entered the warning region. In the FIG. 9 case, nozzle Nos. 4, 5, and 8 have exceeded the warning criteria, and accordingly maintenance instructions with respect to the equipment and the circuit boards are given to cause various checks to be carried out, including nozzle cleaning checks and cassette checks, and also to cause various operations to be carried out, including filter replacement against filter blinding, and nozzle cleaning. Then, operation of equipment is modified so that the inspection results will come within the normal region.
FIG. 10 shows an example of time series analysis of inspection results with respect to monitor items for "component positional shift (in X direction)" at the component mounting unit 2, with warning criteria set at .+-.0.2 mm and judgement criteria at .+-.0.38 mm. Although the measurement results are within the normal region, when inspection measurements exceed the warning criteria, maintenance instructions with respect to the equipment and the circuit boards are given to cause various checks to be carried out, including checks of reference pins for positioning in holes of circuit boards and nozzle cleaning checks, and also to cause shift amount corrections to be made, including data offset corrections with respect to mounting position NC data. Then, operation of equipment is modified so that the inspection results will come within the normal region.
FIG. 11 shows an example of solder inspection error cumulative percentages by circuit numbers with respect to monitor items, such as small height of component, rotational shift in right direction, rotational shift in left direction, bridge defective, and edge detection defective at the soldering unit 3, with warning criteria and judgement criteria established according to cumulative percentages of such items as "small height of component", "rotational shift in right direction", "rotational shift in left direction", "bridge defective", and "edge detection defective" which have entered the warning regions. In the case of FIG. 11, circuit board No. N413 whose cumulative percentage of entry into the warning region is highest of all exceeds the warning criteria and accordingly maintenance instructions with respect to the equipment and the circuit boards are given to cause checks to be carried out, including solder checks, PCB checks, and furnace temperature profile checks, and also to cause changes to be made, including heater temperature change, conveyor speed change, and N.sub.2 quantity change. Then, operation of equipment is modified so that the inspection results will come within the normal region.
FIG. 12 shows an example of time series analysis of inspection results with respect to monitor items for "component positional shift (in X direction)" at the soldering unit 3, with warning criteria set at .+-.0.1 mm and judgement criteria at .+-.0.2 mm. The measurement results are in excess of the warning criterion of .+-.1 mm, and accordingly maintenance instructions with respect to the equipment and the circuit boards are given to cause checks to be carried out, including profile checks, PCB checks, and solder checks, and also to cause corrections of reflow conditions to be made, including heater temperature changes. Then, operation of equipment is modified so that the inspection results will come within the normal region.
On the basis of the foregoing inspection data analysis results, a correlation analyzing part 16 at the control part 17 will perform quality control operations as detailed below.
On the basis of analysis data from printing data analyzing part 7, mounting data analyzing part 11, and soldering data analyzing part 15, the correlation analyzing part 16 analyzes correlations of defective factors for defect occurrences at various processes with respect to monitor items. Then, on the basis of the analysis results of such correlations, the correlation analyzing part 16 issues an operation control instruction to at least one of the solder paste printing device 4, mounting device 8, and reflow furnace 12 for a dynamic change of operation to thereby increase the yield of acceptables.
By way of example, monitor items for chip orientation (manhattan phenomenon) are taken up for explanation of correlations between various processes. If the rate of heating at the reflow furnace 12 is increased too much, an abrupt rise will occur with the solder temperature. In this case, if there is any solder print shift or component mounting shift, terminals 19 of a chip component 18 are mounted offset from the position of solder 20 and then, as a result of such abrupt change in the solder temperature, its smaller volume side of solder 20 melts first. Accordingly, the terminals 19 are drawn under the surface tension of the solder, so that there occurs a chip orientation condition, as shown in FIG. 13.
FIG. 14 shows a chart of defective factors. The solder paste printing process, component mounting process, and N.sub.2 reflow process all involve factors for a chip orientation defect. However, in order that a chip orientation defect may be detected in the inspection process, a component must be mounted, which takes place in the component mounting process and N.sub.2 reflow process. Therefore, the presence of any chip orientation defect as monitor item is checked by inspecting the component mounting process and N.sub.2 reflow process. When, at these processes, the frequency of chip orientation defect occurrences exceeds the warning criterion, maintenance instructions are given with respect to the equipment and the circuit boards for the correction of chip orientation defects. Such instructions are given for correction with respect to print shift, print thickness, etc., when given to the solder paste printing process; for correction with respect to mounting shift, fitting-in. etc. when given to the component mounting process; and for improvement heating rate, air velocity, etc. when given to the N.sub.2 reflow process. In this way, conditions of operation of respective equipment units are dynamically changed so as to eliminate chip orientation defects.
Conversely, when inspection results at the solder paste printing process are in the warning region, if any print shift, for example, is found in excess of the warning criterion, in order to prevent the occurrence of any chip orientation defect at the component mounting process and N.sub.2 reflow process, on the downstream side of this detection process, dynamic controls with respect to equipment are effected for correcting the component mounting position at the component mounting process so as to nullify the detected print shift, and for reducing the heating velocity at the N.sub.2 reflow process. Results of collective analysis and time series analysis of inspection data by the analyzing parts 7, 11, 15 of the control part 17 with respect to the foregoing monitor items, and also of distribution analysis of inspection analysis values as shown in FIG. 15 (analysis of component mounting positional shifts in FIG. 15), together with inter-process relationship analysis results of defective factors with respect to the monitor items of each process which are based on the analysis results with respect to the inspection data and obtained by the correlation analyzing part 16, are incorporated, in parallel with production, into a data base, and this permits monitor display and copying. Thus, it is possible to quickly carry out various analyses, such as quality trend analysis, historical quality analysis, and quality source analysis, for any period of time, thereby to promptly grasp causes of defects. Through repetition of these operations it is possible to provide warning criteria on the basis of which the analyzing parts 7, 11, 15 and correlation analyzing part 16 are caused to carry out quality control, whereby proper measures for defect prevention can be carried out prior to the occurrence of any defect.
In the examples shown in FIGS. 13 and 14, correlation analysis by the correlation analyzing part 16 is explained with respect to a chip orientation defect called "Manhattan phenomenon". Several monitor items are involved such as "solder bridge" and "component positional shift". With respect to any monitor item such that the cause of defect exists over some processes, correlation analyses can be carried out by the correlation analyzing part 16 with good effect as shown in FIG. 15.
In FIG. 16, "(first)" refers to inspection under defect judgement criteria, and "(second)" refers to inspection under warning criteria. That is, quality control operations through inter-process correlation analysis of inspection results, as shown in FIG. 16, are carried out in such a way that in printing and mounting inspections, inspection is made according to the warning criteria, and in soldering inspections, inspection is made according to the defect judgement criteria.
Use of such criteria is advantageous in that where "solder blur" exceeds the warning criterion during a printing inspection but is within the normal region during a mounting inspection, maintenance care is effected with respect to the equipment and circuit boards on the basis of such excess found over the warning criterion during the printing inspection, whereby the mounting inspection is passed and possible occurrence of any solder bridge defect can be prevented during the process of a soldering inspection.
Where a printing inspection is passed but "mounting shift" exceeds the warning criteria during a mount inspection, maintenance care is effected with respect to the equipment and circuit boards on the basis of such excess found over the warning criterion during the mounting inspection, whereby possible occurrence of any chip shift can be prevented during the process of a soldering inspection.
Where "solder blur" exceeds the warning criterion during a printing inspection and "mounting shift" exceeds the warning criterion during a mounting inspection, maintenance care is effected with respect to the equipment and circuit boards on the basis of such excess found over the warning criterion during the printing inspection, and of such excess found over the warning criterion during the mounting inspection, whereby possible occurrence of any "Manhattan phenomenon" can be prevented during the process of a soldering inspection.
Setting of above described monitor items need not be made with respect to all processes and, therefore, it may be arranged that monitor items are set for any selected processes so that operation control instructions may be given with respect to the selected processes.
According to the above described prior art arrangement, quality control on the basis of inspection data analysis by the data analyzing part with respect to the monitor items, and quality control on the basis of the result of correlation analysis by the correlation analyzing part with respect to individual processes involved, are carried out for each production line of the mounted circuit board production system 1. Therefore, inspection data to be used for quality control purposes are limited to only data available within each particular production line per se. As a result, available inspection data are small in number, so that too much time is required for accumulation of inspection data before any quality control can be effectively made on the basis of correlation analysis results.
In particular, a flexible production system in which a large variety of products are produced in limited quantities involves an issue such that the lack of inspection data does not permit effective quality control by correlation analysis results.
Where some trouble has occurred in a mounted circuit board producing system having a plurality of mounted circuit board production lines, so that changes are required with operating programs, libraries, circuit board producing conditions, and inspection conditions, for each line, it is necessary to analyze actual production data and inspection data of the particular line in which the trouble or the like has occurred and then carry out the above changes with the line and, in addition, to separately analyze actual production data and inspection data of the other lines and separately carry out such related changes.